The present invention relates to an additive to water for fire prevention and fire extinguishing, and further relates to the use of a cross-linked polymer with thickening properties as the primary component of the additive.
Water is the most commonly used substance to extinguish fires and to prevent the spread thereof to surrounding structures. Water has several effects on a fire, such as heat removal and oxygen deprivation. When structures adjacent to a fire are soaked with water, the fire must provide enough heat to evaporate the water before the structure can reach its combustion or ignition temperature. A significant disadvantage to the use of water to soak adjacent structures is that the water that does not soak into the structure tends to run off or fall unused upon the ground, thus wasting the water. Another disadvantage is that the water that does soak into the structure provides only a very limited protection against the fire because the structure may only absorb a limited amount of water, and that water is quickly evaporated. Also, significant manpower must be expended to resoak those structures from which the water is evaporated to provide continuing fire protection.
A further disadvantage to using water in fighting fires is that a significant amount of the water does not directly fight the fire because of the aforementioned run-off. Another disadvantage to using water in fighting fires is that water sprayed directly on the fire evaporates at an upper level of the fire, with the result that significantly less water than is applied is able to penetrate sufficiently to extinguish the base of the fire.
To address the above disadvantages with water, U.S. Pat. No. 5,190,110, issued to von Blucher et al, uses absorbent polymers with particle sizes from 20 to 500 microns dispersed in a water miscible media to be incorporated into the water by stirring or pumping, such that the resultant viscosity does not exceed 100 mPa.multidot.s. This system contains discrete gel particles that absorb water, without being soluble in water, and are entrained in the water for application directly to a fire. The '110 patent teaches directly away from using any materials that result in a higher viscosity than 100 mPa.multidot.s. The usual method of applying the additive in the '110 patent is to pre-mix the solid granule particles with the water source. An alternative method that is disclosed is to add the solid granule particles directly in advance of the nozzle while they are in the non-swollen condition. This alternative does not provide sufficient time for the particles to swell, and the viscosity is not increased sufficiently to allow the particles to adhere to surfaces. This is akin to just throwing the solid polymer particles on the fire in the hopes that they will swell after application.
Likewise, U.S. Pat. No. 4,978,460, issued to von Blucher et al, addresses the problem of using solely water to extinguish fires. The solid polymer particles of the '460 patent are encased by a water-soluble release agent to avoid any agglutination of the particles. The time that it takes for these solid granular particles to expand from the absorption of water ranges from ten seconds to several minutes. When fighting a fire with typical hose lengths, ten seconds is longer than practical for the water to be retained in a fire hose. Additionally, in order to achieve the desired water absorption, it was necessary to introduce 200 grams of the product of the '460 patent into each liter of water. At this rate, approximately 835 pounds of the product would be required for a typical 500 gallon pumper.
U.S. Pat. No. 3,758,641, issued to Zweigle, also discusses the use of solid granular polymer particles with high water absorption in firefighting applications. Use of these particles is best accomplished with special, additional firefighting equipment.
The state of use of absorbent polymers in fighting fires remains that due to the solid, granular nature of the particles, it is difficult, if not impossible, to use these polymers in many firefighting applications. For example, if a natural source of water, such as a creek or a river, is to be used as the water source, it is impossible to pre-mix the polymer and batch add it to the water source, as necessary in traditional applications, in order to draw it off to use to combat fires. By pouring the additive into a stream or river, most of the additive will simply flow past the point of suction of the water for use in combating fires. Likewise, because of the particulate nature of the state-of-the-art firefighting, water-absorbent polymer, eduction of such polymer into the standard firefighting hose with standard equipment is nearly impossible. The solid nature of the polymers promote agglutination of the particles and subsequent blockage of the flow of the water. Alternatively, it is also sometimes necessary to provide "pumps and spray nozzles adapted for handling for such materials" in the use of these solid granular particles (see, for example, Zweigle '641). Additionally, the smallest particle size disclosed by the current water-absorbent polymer art for use in firefighting is no less than 20 microns.
Thus, it becomes desirable to develop a water-absorbent polymer that is not limited in application, as are the above polymers, by a solid, granular state. Such a water-absorbent polymer for use as a yarn coating is disclosed in U.S. Pat. No. 5,264,251, issued to Geursen et al.
The polymer provided in Geursen provides substantial water absorption and can be processed in stable water-in-oil emulsions. Such an emulsion allows this absorbent polymer material to be applied to a yarn. It is important for the polymer formed in such a water-in-oil emulsion in the Geursen patent to retain a relatively low viscosity. This is critical to the application of the polymer to the yarn.
Thus, it would be desirable to provide a water-absorbent polymer that will quickly swell in the presence of water for application in firefighting situations. Such a composition would be mixable with the water source and desirably be eductable into a fire hose using standard firefighting equipment to allow its use in a very wide variety of firefighting situations, and also have sufficient viscosity to enable it to adhere to vertical and horizontal surfaces.